Locking and pressure release mechanism for hydraulic motors



B. N. ASHTON 2,576,554

LOCKING AND PRESSURE RELEASE MECHANISM FOR HYDRAULIC MOTORS Nov. 27, 1951 Filed Feb. 25, 1946 5 Sheets-Shegzt 1 Nov. 27, 1951 B. N. ASHTON 2,576,554

LOCKING AND PRESSURE RELEASE MECHANISM FOR HYDRAULIC MOTORS Filed Feb. 25, 1946 5 Sheets-Sheet 2 Nov. 27, 1951 B. N. ASHTON 2,575,554

LOCKING AND PRESSURE RELEASE MECHANISM FOR HYDRAULIC MOTORS Filed Feb. 125, 1946 3 Sheets-Sheet 5 jy 44-1 #w Hf/ahizays Patented Nov. 27, 1951 LOCKING AND PRESSURE RELEASE MECHA- NISM FOR HYDRAULIC MOTORS Benjamin N. Ashton, Kingston, N. Y" assignor to Electrol Incorporated, Kingston, N. Y.,,a, om

ration of Delaware Application February 25, 19416, SerialNo: 649,851

9 Claims. 1

This invention relates to fluid operatedmotors, and it relates particularly to improvements in hydraulic jacks of the cylinder and reciprocating piston type.

An object of the invention is to provide hy draulic jacks with mechanisms for locking, the piston at one or both ends of th stroke of the piston and for relieving the pistonand cylinder of pressure when the piston is locked.

Another object of the invention is to provide hydraulic jacks or lifting motors in which the piston can be displaced by means of fluid pressure to one end of the cylinder and then locked to the cylinder and relieved of fluid pressure.

A-further object of the invention is to provide hydraulic lifting jacks that may be locked in retracted position and may be projected to an extended position while retaining the ability to be varied in overall length while in. the said extended position.

.An additional object of the invention is to provide hydraulic lifting jacks suitable for use with retractable landing gear and the like, said jacks being variable: in length while inan extended condition and under hydraulic pressure to compensate for variation in length of the olee land, ing gear struts and for variation in inflation of the tires.

Other objects of the invention will become ap parent from the following description of typical forms of hydraulicjacks embodying the :present invention.

vSuch hydraulic jacks are provided with pressure-responsive mechanisms for releasably looking theepiston to the cylinder at one or both ends of the cylinder and with a valve means that is opened as the piston is locked to the cylinder to reliev-ethe piston and the cylinder of fluid pressure.

More particularly, the locking mechanism for the piston may include a series of locking elements, such as balls, that are carried by and are displaeeable radially outwardly in the piston into engagement with recesses or a channel. in the interior of the cylinder by means of a slidable lock ing member mounted in the end of the cylinder. The locking member is arranged to enter a recess in the piston near the end of the piston stroke to force the balls partially into the recess to lock the piston to the cylinder. The piston member is displaceable by means of fluid pressure to release the balls for retract-ion into the piston, thereby unlocking the piston and allowing it to be displaced axially of thecylinder.

The fluid pressure exerted .on' the piston may be relieved when the piston is in its locked position, by meansof avalveinterposed between a relief portin the cylinder and the interior of the cylinder on thepressure side of the piston. The valve mechanism is so arranged that when the piston and th locking member move into position to lock the .piston to. the cylinder, the Valve is opened, thereby diverting the pressure fluid to the relief port and relieving the cylinder andithe piston from pressure.

When it is desired touse .J'aciks of the tyn mbodying thepresent invention in connection with a. mechanism that is to be locked in two different positions, the hydraulic jack may be provided with locking mechanisms. and pressure relief valves at opposite ends. In other cases, it may be .desirableto provide alock at only one end vof the Cylinder, for example, for lockin the piston in its innermost .or' retracted position.

The inventionmay be utilized with ajack that is used solely tor lifting purposes such as, for example, for lifting the landing gear of an air-' plane which isextended by gravity. In this case, only one locking mechanism. is provided. The piston-in this .form of jack maybe forced outwardlyor extended by. means of hydraulic pressure or gravity. One form oithe invention includes .a piston rod that is 'slida'bly coupled to the piston so that it. is capable of movement relatively thereto axially of the cylinder. sucha' piston rod and piston arrangement permits variation in the overall length of the hydraulic jack, permitting the jack to adjust itself to variations in the length of the ,shockabsorbing struts and to the mflation of he tires on the landin ar.

For .a better understanding of the present inventionreierence maybe had to the accompanying drawings in which:

Figure l is .a plan view of a typical .form of hydraulic. jack haying locking and pressure relief means at bothends thereof;

Figure .2 is a view in section taken on'line 2-2 of Figure 1;

Fi u e 3 a view in elevation of the rig-hthand end of the hydraulic jack as viewed in Fig-urea;

i ured ista view in side elevation of a modifid form of hydraulic jack having a locking mechanism anda pressure relief means at one end. only, the piston rodlbeingof variable length;

Fig-urea) is .a view in elevation of. the left-hand endz-otzthe-.modified -form of hydraulic jack as viewed in: Figure 4.;

,Figf re fi is a view insection taken on :line 6: 6-

of Figure 4; and

Figure 7 is a view in section of a portion of the jack shown in Figure illustrating details thereof.

The form of hydraulic jack illustrated in Figure 1 includes a tubular cylinder In which is provided at opposite ends with caps II and I2 screwed on the ends of the cylinder and sealed thereto by means of suitable sealing rings [3 and M. The cap I2 is provided with a pair of spaced apart lugs l5 and IE on the end thereof permitting the cylinder to be connected pivotally to a suitable supporting structure, not shown.

The cap H is provided with an annular collar l1 within which is slidably received a piston rod l8 of generally cylindrical shape. The collar I! may be provided with suitable sealing gaskets or packings IQ for preventing leakage therethrough.

One end of the piston rod I8 is provided with a generally cylindrical piston having a groove 20a therein for receiving a piston ring or, as

illustrated, a rubbery toroidal rin 2| for sealing the piston to the wall of the cylinder ID. The piston is further provided with annular flanges 22and 23 at opposite ends thereof which are provided with a plurality of radially extending openings 24 and 25 within which are received a plurality of steel balls 26 and 21. The balls 26 and 21 are retained in the openings 24 and 25 by means of shoulders 28 and 29 on the piston partially underlying the recesses.

As shown in Figure 2, the balls 21 cooperate with an annular recess 30 formed by a channel member 3| mounted between the end of the cylinder l0 and a shoulder 32 on the cap member 12, the recess 30 being of such depth as to partially receive the balls 21'. The opposite end of the cylinder I0 is provided with a similar channel member 33 for receiving the balls 26 to lock the piston at this end of the cylinder.

The piston 26 may be locked at either end of the cylinder ID by means of slidable piston-like locking members 34 and 35 which are mounted within the caps l2 and H respectively and are capable of limited axial movement therein. The locking member 34 fits snugly within the cap member l2 and is provided with grooved flanges 36, 31, and 38 spaced longitudinally of the piston which contain toroidal rubbery sealing rings 39 for sealing the piston 34 at spaced apart zones to the interior of the cap. The locking member 34 also includes a projecting annular portion 40 of smaller diameter than the exterior diameter of the piston 20. The portion 49 is received snugly within the flange 23 when the piston 29 is at the right hand end of the cylinder Ill. The projection 40 is so arranged that it will engage the balls 21 and force them partially into the recess 30 to lock the piston at the end of the stroke. The locking member 34 may be urged toward the left by means of a spring 4| disposed in a central recess therein and engaging the end of the cap l2 or by means of a series of smaller springs received in bores extending parallel to the axis of the piston.

The locking member 35 that cooperates with the locking balls 26 is similar to the locking H ried by the locking member 35 to prevent leak age therethrough.

In order to reciprocate the piston 20 lengthwise of the cylinder ID, the caps II and I2 are provided with suitable inlet anddischarge or return ports. The cap I2 is provided with an enlarged boss or projection having two staggered ports 46 and 47 therein and an oppositely extending boss or projection 48 having a port 49 therein. The port 46 may be connected through a suitable selector valve V to a source of fluid under pressure and communicates with the interior of the cylinder 10 through a groove 46a to the left of the flange 36. The port 41 may be connected through the return port of the selector valve to a return line 0 for the system. The flange 36 is interposed between the port 46 and the port 49, and the flanges 31 and 38 are disposed on opposite sides of the port 4'! for preventing direct communication between that port and the ports 46 and 49.

The port 49 is connected to the low pressure side of the system, for example, to the inlet of a pump.

The cap H similarly is provided with three ports 56, 5|, and 52, the port 52 being connected to the conduit 0 at the low pressure side of the system, the port 5i being connected through the selector valve V to the pump P and to the port 41 at the opposite end of the cylinder by means of the conduit 0 The ports 50, 5|, and 52 are separated by suitable sealing flanges on the locking member 35 like the flanges 36, 31, and 38 on the member 34. The port 5! corresponds to the port 46; the port 50 to the port 41; and the port 52 to the port 49. The port 56 is connected also to the port 46 at the opposite end of the cylinder by the conduit 0 and to the selector valve V by means of the branch conduit 0 for a purpose to be described.

With the above described arrangement of the ports, when pressure is applied to the piston through the port 46, and the pressure at the port 5| is relieved by means of the selector valve, the locking member 34 is forced to the right, thereby releasing the balls for inward movement. Inas much as the port 46 communicates with the interior of the cylinder to the left of the locking member 34, it will force the piston 26 and the piston rod l8 to the left until the piston 26 strikes the locking member 35 displacing it to the left until the balls 26 enter the recess 33, at which time they are displaced outwardly by the return of the locking member 35 to the right under the biasing action of the springs 43. The piston 29 may be released and moved to the right by applying fiuid pressure at the port 51 and relieving the fluid pressure at the port 46 by means of the selector valve V, as shown in dotted lines.

In order to relieve the piston and the cylinder of pressure when the piston has moved to locking position at one end of the cylinder, the locking members 34 and 35 each may be provided with a suitable relief valve construction. This valve construction, as illustrated, includes a recess 53 formed in the body of the piston member 34 having opposite ends communicating with the interior of the cap I2 on opposite sides of the flange 3i and connecting the port 41 to the port 49. The flange 37 may be provided with a suitable internal bore 54 having a right hand edge forming a valve seat 55 which cooperates with a poppet valve 56. The valve is mounted on a valve stem 51 which is slidably received in a bore 58 extending parallel to the axis of the piston member 34. The valve stem 57 extends slightly beyond the face of the projection 40 when the valve is seated.

Thevalve 56 is normally urged tothe left by means of a spring 59 that engages the valve 56 and a plug. member 60 slidably mountedin a bore-=61 in alignment with the bore 58. The plug 60* is provided with a pin 6la. adapted to engage the end of the cap [2 and thus can adjust itselfrelatively to the valve plug. The plug member 6! may be provided with sealing means for preventing leakage thereby. The spring 59 normally retains the valve plug 56 seated except when an excessively high pressure is present in the cylinder, as, for example, when the. pressure fluid therein expands due to increased temperature conditions and when the piston 20 engages the valve stem 51.

The valve 56 and the valve seat 55 are. inter..- posed between the port and the port 47. When thepiston moves to the right as viewed in Figure 2 under the pressure of fluid introduced through the port 5!, the balls 2? will. engage the projection 40 on the locking member 34 and will. move it: to the right until the balls come into alignmentto the recess 38, at which time they are moved radially outwardly by the movement of the locking member 34 to the left. As the lock ing member 34 moves toward the left, the valve plug 56 is unseated and connects the ports-41 and 49. Inasmuch as the port 41 is connected to the pressure port 5! through which fluidis admitted to force the piston 20 to the right, and the port 49 is connected to the return line, the fluid is bypassed from the interior of the cylinder H]. to the return line, thereby relieving the piston 20 of pressure.

The locking member 35 is provided with a similar valve and valve seat assembly 63 so that the same action takes place upon movement of the piston to the left.

The piston rod. l8 may be coupled in any desired way to mechanism tobe operated- For example, a coupling yoke member 64 may be secured to the end of the piston rod.

The jack illustrated in Figures 4 to '7 is similar to that described above; with the exception that this jack is utilized only for lifting. operations and thus is provided with alock'ing mechanism and a pressure relief valve like those described above, at only one end. This form of device includes a cylinder 70 having caps H "and 1-2 at theopposite ends thereof. The .cap 12 is provided with the ports l3, l4, and 15' connected respectively to an inlet or pressure port T6 in the cap H by means of the conduit c a source: of fluid under pressure, for example, the pump: 10

by means of a conduit and the return line c of the hydraulic system. The port 16 is likewise adaptedto be comiected to a source of fluid under pressure through a conduit 0 a suitable selector valve V by-means of which fluid can be directed selectively to one of the ports 14 and 16 while theother of these ports is relieved of fluid pressure.

The device includes a reciprocating piston 11 which cooperates with the slidable lock member 18 having a bypass valve assembly 19 therein like that in the lock member described above. The slidable lock member 18 and the piston 'l-I' are also provided with ball and recess locking means 86, as described above.

In this form of the invention, a tubular, open end piston rod 8! extends slidably through the piston 11 and is provided with an enlarged head 832. A toroidal ring 83 is mounted in a recess 84 in the piston I! and engages-the piston rod 8h Vlfilthin the piston rod 81 is a second-piston rod- 'as hav'ingapiston 86 thereon. Thepiston rodfl is slidably received in, and. sealed to thecap H.

A suitable eye coupling member 81 may be secured to the end of the rod 85 in ordertocon nect it to an apparatus or a Weight to be lifted.

In order to allow the piston rod 81 to be pro j'ected by gravity, a sealing ring. assembly 89 is mounted between the-ball locking assembly 88 and "thecylindrical surface 90 on the locking piston 18.. Also a ring seal assembly 91 is positioned tothe right of the port 14 to prevent leakage around the outside of the ball lock 80. Inasmuch as these seals prevent leakage past the ball lock and the locking piston 18, the effect of liquid pressure at the port 14 is to displace thelocking piston 18 to the left, thereby freeing the piston for movement to the right under gravity or :externally applied stresses.-

In operation, when the fluid under pressure is introduced through the-port 14 and the port-"I8 is relieved of pressure as indicated by the dotted line position of the selector valve, the locking member 18 will be forced to the left, thereby-freeingthe locking mechanism and allowing-the piston 17 to move to the right. The piston rod 8i and the piston 82 may move relativelyto the piston 11 and likewise the piston rod 8=5 and the piston 86may be-stro-ked back and forth in the piston rod B l Air displaced by the'movement of thepiston rod 8| and the piston 86- may escape or be admitted through thehole 18a in the locking member 18 and the hole 12a, in the cap 1 2..-

When fluid under pressure is supplied to the port 16 and the port" isrelieved of pressure, the piston H is moved to the left, thereby drawing the piston-rod 8| along with it and displacingthe piston member 18 sufficiently to-permit. the balls to lock the piston to. the cylinder. In the locked position, the valve assembly 19 is opened-thereby bypassing the fluid pressure applied to the port 1-6 and to the port 13 through the return line 15 and relieving the cylinder to the right of. the piston H of fluid pressure. Astop rod 92 is fixed tothescap- 1.2 to prevent displacement of the locking piston 18, if the momentum of the rod 8| tends to carry it too far to the left. The hydraulic jack disclosed in Figures 4 to? is a lifting jack. andzfor that reason, pressure is applied to the piston only through the port 16 to lift an element supported on the eye 81. The piston rods and the piston are moved to the right, as viewed in Figure 6, by the weight of an article suspended thereon: and not by fluid pressure againstthe lefthan d end of the piston 11.

The hydraulic fluid is supplied. to the port H to release the locking mechanism so that the piston and the piston rods can travel to theright.

The looseconnection between the piston :rod 8| and the piston 1'! permits relative movement between them to accommodate changes in the length of the device with which they are associated; The sliding connection between the piston rod'8l and the rod serves the same purpose; Neitherof the piston rods 8| or 85 is forced by the action of the hydraulic fiuid in either direction. In other words, they are capable of moving relative to each other and to the piston 11 when the piston is at the right-hand end of the cylinder, as viewed in Figure 6. Such relatively movable piston rods are useful in connection with aircraft landing gear to permit unrestricted movement of the oleo strut. It is useful'also when the fullstroke of the piston might exceed the lifting distance-or when the obj act-being lifted must move independently of the piston 11.

.From the preceding description of typical forms of devices embodying the present invention, it will be apparent that I have provided hydraulic jacks that are capable of being locked in one or more positions and which in such locked positions are relieved of the pressurerof the fluid so that a quick response of the jack to operation of the selector valve is assured.

It will be understood that the size and shape of the jacks may be modified and that the type of relief valve and spring actuating mechanism for the locking piston member may be modified considerably. Therefore, the forms of the invention disclosed herein should be considered as illustrative and not as limiting the scope of the following claims.

.I claim:

1. A hydraulic motor comprising a hollow cylinder, a piston reciprocable axially of said cylinder inlet ports at opposite ends of said cylinder for supplying fluid under pressure to said cylinder, a fluid return port at one end or" said cylinder isolated from said inlet ports, a discharge port at said one end, said discharge port being connected to the inlet port at the opposite end .of said cylinder, a member between said discharge and return ports having a passage therein connecting said return and discharge ports, valve means in said passage, said valve means being normally biased to'closed position to disconnect said discharge port from said return port, and means on said valve means engageable by said piston when the latter is at said one end for opening said valve means to connect said discharge and return ports and by-pass the fluid from the inlet port at said opposite end through said discharge and return ports to relieve said piston of the pressure urging said piston toward said one end.

2. A hydraulic motor comprising a hollow cylinder, a piston reciprocable in said cylinder, an inlet port for supplying fluid under pressure to one end of said cylinder, a discharge port at the other end of the cylinder, means to connect said inlet port to said discharge port, a return port, a return line connected to said return port to discharge liquid from said cylinder, a partition in said cylinder between said discharge and return .ports, said partition having a passage therein connecting said discharge port to said return port, and a valve in said passage, said valve being normally biased to closed position to prevent communication between said discharge port and said return port and means on said valve engageable by said piston to open the valve when the piston is at said other end of said cylinder to. connect the inlet port to the return port through said passage to by-pass liquid from said inlet port to said return port to relieve the piston of fluid pressure.

3. A hydraulic motor comprising a hollow cylinder, a piston reciprocable in said cylinder, means for supplying fluid under pressure to opposite ends of said cylinder, a radially movable member carried by said piston, a recess at one end of said cylinder for partially receiving said member to lock said piston to said cylinder, a piston-like locking member in said one end of said cylinder and having limited sliding movement relatively thereto, said locking member being engageable with said radially movable membeer to urge it into said recess and being movable in response to fluid pressure for disengaging said radially movablemember to release said piston, means for discharging fluid from said one end of said cylinder, means at said one end form ingv a port adapted to be connected to the fluid supply means at the opposite end of said cylinder and valve means normally biased to closed position carried by said locking member and interposed between said port and said fluid discharging means, said valve being opened in response to movement of said piston to said one end of said cylinder.

4. A hydraulic motor comprising a hollow cylinder, a piston reciprocable in said cylinder, means for supplying fluidunder pressure to 0pposite ends of said cylinder, a radially movable member carried by said piston, a recess at one end of said cylinder for partially receiving said member to lock said piston to said cylinder, a piston-like locking member in said one end of said cylinder and having limited sliding movement relatively thereto, said locking member being engageable with said radially movable member, to urge it into said recess and being movable in response to fluid pressure for disengaging said radially movable member to release said piston, means for discharging fluid from said one end of said cylinder, means at said one end forming a port adapted to be connected to the fluid supply means at the opposite end of said cylinder and valve means in said cylinder normally biased to closed position interposed between said port and said fluid discharging means, said valve being opened in response to movement of said piston to said one end of said cylinder.

5. A hydraulic motor comprising a cylinder, a piston reciprocable in said cylinder, supply ports for supplying fluid under pressure to said cylinder on opposite sides of said piston, a fluid return port at one end of said cylinder, said return port being isolated from said supply ports, another port in said one end of said cylinder communicating with the supply port at the opposite end of the cylinder, a member in said one end of said cylinder interposed between said another port and said return port and having a passage therethrough connecting said another port and said return port, a normally closed valve in said passage between said return port and said another port to prevent flow of fluid from said another port to said return port, and means responsive to movement of said piston toward said one end of said cylinder for opening said valve to divert the fluid from said supply port in said opposite end of said cylinder to said return port to relieve the piston of pressure.

6. A hydraulic motor comprising a cylinder, a piston reciprocable in said cylinder, cooperating means on said cylinder and said piston for looking the latter to one end of said cylinder, means for supplying fluid under pressure to opposite ends of said cylinder, a movable piston-like looking member in said one end of said cylinder, said locking member being movable relatively to said piston to actuate said locking means to lock and release said piston and cylinder, means forming a pair of ports at said one end of said cylinder, one of said ports adapted to be connected to a return conduit and the other adapted to be connected with the fluid supply means at the opposite end of said cylinder, a normally closed valve interposed between said ports, and means responsive to movement of said piston into locked position for opening said valve.

7. A hydraulic motor comprising a cylinder, a piston reciprocable in said cylinder, cooperating means on said cylinder and said piston for lockh s thelatterjo-one end of said cylinder, means for supplying fluid under pressure to opposite ends of said cylinder, a movable piston-like locking member in said one end of said cylinder, said locking member being movable relatively to said piston to actuate said locking means to lock and release said piston and cylinder, means forming a pair of ports at said one end of said cylinder, one of said ports adapted to be connected to a return conduit and the other adapted to be connected with the fluid supply means at the opposite end of said cylinder, a normally closed valve carried by said locking member interposed between said ports, and means responsive to movement of said piston into locked position for opening said valve.

8. A hydraulic motor comprising a cylinder, a piston reciprocable in said cylinder, cooperating means on said cylinder and said piston for looking the latter to one end of said cylinder, fluid pressure responsive means for locking and unlocking said locking means, means for supplying fluid under pressure to said cylinder on opposite sides of said piston, means forming a fluid return port at said one end of said cylinder, a normally closed valve in said cylinder and interposed between said return port and the fluid supply means connected to the opposite end of said cylinder, and means responsive to movement of said piston into locked position for opening said valve to divert the fluid from said opposite end of said cylinder, and a tubular piston rod slidably connected to said piston and movable relatively thereto.

9. A hydraulic motor comprising a. cylinder, a piston reciprocable in said cylinder, cooperating 10 means on said cylinder and said piston for locking the latter to one end of said cylinder, fluid pressure responsive means for locking and unlocking said locking means, means for supplying fluid under pressure to said cylinder on opposite sides of said piston, means forming a fluid return port at said one end of said cylinder, a normally closed valve interposed between said return port and the fluid supply means connected to the opposite end of said cylinder, and means responsive to movement of said piston into locked position for opening said valve to divert the fluid from said opposite end of said cylinder, a first tubular piston rod slidably connected to said piston and movable relatively thereto, and a second piston rod slidable in said first piston rod and having a connecting element thereon.

BENJAMIN N, ASHTON.

REFERENCES CITED The following references are of record in the -iile of this patent:

UNITED STATES PATENTS Number Name Date 1,582,468 Heald Apr. 27, 1926 2,233,521 Ernst Mar. 4, 1941 2,295,961 Meyer Sept. 15, 1942 2,297,902 Levy Oct. 6, 1942 2,360,535 Ashton Oct. 17, 1944 2,451,089 Hunter Oct. 12, 1948 FOREIGN PATENTS Number Country Date 500,673 Great Britain Feb. 14,4939 

